Credit Report

My ex has done a credit search in my name.. He says he just wanted to make sure I was not accumulating joint debt. what are my rights

I doubt he has been able to do this - there are a series of passwords that get sent out before you are able to access your reports and the letters would go to the person who's report is required.

More than likely he has done his own credit check on his own name which would show up an financial associations with another person.

It should be impossible for you to take out credit in joint names unless you're prepared to commit fraud by forging his signature! with this in mind, you might want to check what's going on yourself....

The reason I found out he had done the search was I received a letter from Experian thanking me for opening my account. I have cancelled the account but wonder were I stand legally

Its actually pretty easy to do this.
You dont need passwords etc all you need to know is your DOB and addresses for the last few years and you can set up an account on experian or equifax.

It shows credit in your name and credit in your exs as well as joint so he could have actually done this on himself and you would have been 'financially associated' with him on his own report. No reason for him to do it on your OWN other than to find out if you had any lone debt??!!
You would need to check the disclaimer on the website to see what the privacy terms are.
This wont affect your credit but he has been able to see exactly where you stand financially..well, according to one agency anyway.